MRI (magnetic resonance imaging) is a medical-imaging technology often used by radiologists to produce a sequence, or “time series,” of high-resolution three-dimensional images of human anatomy. MRI is widely used to diagnose or stage disease without exposing a subject to ionizing radiation.
fMRI (functional MRI) is an application of magnetic resonance imaging technology used to identify regions of a subject's brain and identify how those regions respond to a specific stimulus or task. A region may so respond by exhibiting a degree of “activation,” and an fMRI technique that measures such activation responses is known as blood oxygenation level dependent (BOLD) fMRI.
It is possible to construct a generalized three-dimensional map of regions of the brain and that may be superimposed over a three-dimensional MRI image of a brain. When used this way, the map acts like a template that delineates three-dimensional regions of interest comprised by the brain image. Such a generalized template, however, may not accurately identify a region of interest in a specific subject's brain. Furthermore, in some cases, such a template may require extensive “training” with subject-specific data to become reliable, a requirement that may make it impossible to use the template in real time to analyze a stream of fMRI data as it arrives.